1,179 research outputs found
Trapping and detection of single atoms using a spherical mirror
We fabricate a miniature spherical mirror for tightly focusing an optical
dipole trap for neutral atoms. The mirror formation process is modelled to
predict the dimensions for particular fabrication parameters. We integrate the
spherical mirror with a neutral atom experiment to trap and detect a single
atom with high efficiency. The mirror serves the dual purpose of focusing the
dipole trap as well as collection of the atomic fluorescence into an optical
fibre.Comment: 13 pages, 6 figure
State detection using coherent Raman repumping and two-color Raman transfers
We demonstrate state detection based on coherent Raman repumping and a
two-color Raman state transfer. The Raman coupling during detection selectively
eliminates unwanted dark states in the fluorescence cycle without compromising
the immunity of the desired dark state to off-resonant scattering. We
demonstrate this technique using where a combination of
Raman coupling and optical pumping leaves the
metastable state optically dark and immune to off-resonant scattering. All
other states are strongly coupled to the upper levels. We achieve a
single shot state-detection efficiency of in a
integration time, limited almost entirely by technical imperfections. Shelving
to the state before detection is performed via a two-color
Raman transfer with a fidelity of
Collective cavity quantum electrodynamics with multiple atomic levels
We study the transmission spectra of ultracold rubidium atoms coupled to a
high-finesse optical cavity. Under weak probing with pi-polarized light, the
linear response of the system is that of a collective spin with multiple levels
coupled to a single mode of the cavity. By varying the atom number, we change
the collective coupling of the system. We observe the change in transmission
spectra when going from a regime where the collective coupling is much smaller
than the separation of the atomic levels to a regime where both are of
comparable size. The observations are in good agreement with a reduced model we
developed for our system.Comment: 4 pages, 4 figure
Fabrication of Glass Micro-Cavities for Cavity QED Experiments
We report a process for fabricating high quality, defect-free spherical
mirror templates suitable for developing high finesse optical Fabry-Perot
resonators. The process utilizes the controlled reflow of borosilicate glass
and differential pressure to produce mirrors with 0.3 nanometer surface
roughness. The dimensions of the mirrors are in the 0.5-5mm range making them
suitable candidates for integration with on-chip neutral atom and ion
experiments where enhanced interaction between atoms and photons are required.
Moreover the mirror curvature, dimension and placement is readily controlled
and the process can easily provide an array of such mirrors. We show that
cavities constructed with these mirror templates are well suited to quantum
information applications such as single photon sources and atom-photon
entanglement.Comment: 3 page
Action Learning Report 2019: A follow-up to the National Evaluation of The Royal British Legion’s Break Services
In August 2017, a research team at Liverpool John Moores University embarked upon a 12-month transformative evaluation of The Royal British Legion’s (hereafter ‘The Legion’) suite of Breaks Services. This document details the findings of an event-based follow-up project funded by Liverpool John Moores University. Focusing upon the implementation of the Theory of Change Model (TCM) created during this research, this project aimed to:
Work with staff to recognise and maintain strengths of the Service.
To continue processes of action learning beyond the Evaluation. To support Break Services staff in digesting the Evaluation.
To share and explain best practice.
To identify operational activities in response to the findings.
To understand the experience of front-line TRBL Break Service staff and include their voice in management discussions.
To understand the experience of transition for the service as the new strategy is crafted
Smoothed Particle Hydrodynamics Simulations of Apsidal and Nodal Superhumps
In recent years a handful of systems have been observed to show "negative"
(nodal) superhumps, with periods slightly shorter than the orbital period. It
has been suggested that these modes are a consequence of the slow retrograde
precession of the line of nodes in a disk tilted with respect to the orbital
plane. Our simulations confirm and refine this model: they suggest a roughly
axisymmetric, retrogradely-precessing, tilted disk that is driven at a period
slightly less than half the orbital period as the tidal field of the orbiting
secondary encounters in turn the two halves of the disk above and below the
midplane. Each of these passings leads to viscous dissipation on one face of an
optically-thick disk -- observers on opposite sides of the disk would each
observe one brightening per orbit, but 180 degrees out of phase with each
other.Comment: 11 pages. Accepted for publication in The ApJ Letter
The Intrinsic Origin of Spin Echoes in Dipolar Solids Generated by Strong Pi Pulses
In spectroscopy, it is conventional to treat pulses much stronger than the
linewidth as delta-functions. In NMR, this assumption leads to the prediction
that pi pulses do not refocus the dipolar coupling. However, NMR spin echo
measurements in dipolar solids defy these conventional expectations when more
than one pi pulse is used. Observed effects include a long tail in the CPMG
echo train for short delays between pi pulses, an even-odd asymmetry in the
echo amplitudes for long delays, an unusual fingerprint pattern for
intermediate delays, and a strong sensitivity to pi-pulse phase. Experiments
that set limits on possible extrinsic causes for the phenomena are reported. We
find that the action of the system's internal Hamiltonian during any real pulse
is sufficient to cause the effects. Exact numerical calculations, combined with
average Hamiltonian theory, identify novel terms that are sensitive to
parameters such as pulse phase, dipolar coupling, and system size.
Visualization of the entire density matrix shows a unique flow of quantum
coherence from non-observable to observable channels when applying repeated pi
pulses.Comment: 24 pages, 27 figures. Revised from helpful referee comments. Added
new Table IV, new paragraphs on pages 3 and 1
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